The present invention relates to an electrophotographic printer provided with a cleaning device and capable of removing a toner residual on an outer circumference of a photoconductor after transferring the toner to a paper of the electrophotographic printer.
In a conventional electrophotographic printer, an image is formed on the circumference of the photoconductor by the use of a charging unit, an exposing unit, a developing unit and a transferring unit, and the resultant image on the photoconductor is transferred to the paper. The toner residual on the outer circumference of the photoconductor, after the image has been transferred to the paper, is removed by a cleaning device and the toner is supplied afresh to the photoconductor so that the photoconductor can form the image thereon and transfer the image to the paper. The toner is fixed to the paper, to which the image is transferred, by a heat fusing device so that the duplication to the paper is completed and the duplicated paper is thereafter discharged. The toner removed, by the cleaning device is collected and utilized for the next supply.
In order to keep up the quality of the image transferred to the paper, there has been developed recently an electrophotogaphic printer unit comprising a photoconductor, a developing unit and a cleaning device which have respectively their own specific life and are required to have a precise positional relation therebetween. These components can be fabricated as unit, thereby eliminating the adjustment of the positional relation therebetween and rendering each unit replaceable with another unit. The units are formed of synthetic resin, at low cost and with ease since they are expandable.
In the electrophotograhic printer, for the convenience of the duplicating process, the heat fusing device is disposed adjacent to the cleaning device. Since the heat fusing device fixed the image by a heater at a temperature of 130.degree. to 190.degree. C., not a little heat is transmitted to the cleaning device. There is collected toner in the cleaning device. Since the toner begins to melt at a temperature of at least 50.degree., the temperature over 50.degree. does not heat the toner in the cleaning device because of the distance between the heat fusing device and the cleaning device. However, the following problems occur in the electrophotographic printer.
There are disposed a motor and a heat source such as a power supply adjacent to the cleaning device for rotatably driving the photoconductor due to a recent tendency to miniaturize the electrophotographic printer. Hence, the heat applied to the cleaning device is from the heat fusing device and from the heat source such as the motor or power supply. As a result, the heat is sharply increased to exceed a temperature of 50.degree. C. at the portion where the heat source such as the motor or the power supply is disposed in the cleaning device, thereby melting the toner. The melted toner can not be utilized again. If the melted toner is cooled and solidified, the mechanism in the cleaning device is liable to stop, which causes trouble. It is possible to increase the distance between the heat source and the cleaning device but it is contrary to the trend toward miniaturization of the electrophotographic printer.